The present invention relates to a constant speed drive for an output load, such as a pump, fan, etc., and more particularly to a drive which is lead compensated and will anticipate changes in the output speed to the load and make appropriate corrections therefor.
Presently utilized control devices providing a constant speed for a load involve in their simplest form a magnetic pick-up and an electric servovalve. As the control function becomes more sophisticated and sensitive, the system becomes more and more complex in its arrangement and function. Thus, very complex systems have evolved using a tachometer and electrical control circuits. Other systems utilize complex hydraulic valving alone or associated with electrical control circuits. The present invention provides a simplified control system which overcomes disadvantages inherent in many prior known systems.
Among the objects of the present invention is the provision of a constant speed drive for an output load, such as a pump or fan, wherein the complexity of the system is minimized. The system is hydraulic in nture without any electrical connections and the attendant fire hazards.
Another object of the present invention is the provision of a constant speed drive for an output load which has a lead compensation that anticipates the variations in the output shaft speed and initiates appropriate correction for the variation.
A further object of the present invention is the provision of a constant speed drive utilizing a hydraulic circuit with a spool valve controlling actuation of a clutch in the drive line between a constant speed motor and an output shaft to the load being driven. The system can be made as sensitive to speed (pressure) changes as desired by changing the area of the diaphragm in the spool valve.
The present invention relates to a hydraulically-actuated system for speed control of an output shaft driven by a constant speed motor through a clutch. The pressure actuator for the clutch is controlled through a spool valve receiving fluid from a pump driven by the motor. A second pump, driven by the output shaft, provides fluid pressure to an accumulator and to the spool valve; with the various pressures acting upon diaphragms to provide for adjustment of the spool valve.
Further objects are to provide a construction of maximum simplicity, efficiency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.